How to get the inode - no path_lookup

From: rohan.puri15@gmail.com (Rohan Puri)
To: kernelnewbies@lists.kernelnewbies.org
Subject: How to get the inode - no path_lookup
Date: Mon, 13 Aug 2012 15:04:10 +0530	[thread overview]
Message-ID: <CALJfu6P3PD30gQtgMFXqvS9TUO11qs1QTx3H2=vPTYoKuv7-yQ@mail.gmail.com> (raw)
In-Reply-To: <CADDndfMJ2OSGYqWU=En1v4JvGR63PyMpmPYQ3BDTriGsmgiy-g@mail.gmail.com>

On Mon, Aug 13, 2012 at 2:17 PM, Rishi Agrawal <rishi.b.agrawal@gmail.com>wrote:

>
>
> On Thu, Aug 9, 2012 at 12:39 PM, Rohan Puri <rohan.puri15@gmail.com>wrote:
>
>>
>>
>> On Thu, Aug 9, 2012 at 8:45 AM, Rishi Agrawal <rishi.b.agrawal@gmail.com>wrote:
>>
>>>
>>>
>>> On Wed, Aug 8, 2012 at 12:46 PM, Rohan Puri <rohan.puri15@gmail.com>wrote:
>>>
>>>>
>>>>
>>>> On Tue, Aug 7, 2012 at 8:11 PM, Rishi Agrawal <
>>>> rishi.b.agrawal at gmail.com> wrote:
>>>>
>>>>> Hi All,
>>>>>
>>>>>
>>>>> I had a module which used the path_lookup function to print the
>>>>> details of any file's inode. I now want to rewrite that module in order to
>>>>> show some juniors how to write some code in kernel.
>>>>>
>>>>> I am using 3.4.6 kernel, I tried finding out path_lookup but google
>>>>> showed that it has been removed.
>>>>>
>>>>> I tried the following code then which did not work
>>>>>
>>>>> .
>>>>> .
>>>>> .
>>>>> dentry = kern_path_create(AT_FDCWD, filename, &path, 1);
>>>>>
>>>>> if (IS_ERR(dentry)) {
>>>>>               printk("Failed to obtain the dentry");
>>>>>                return;
>>>>>        }
>>>>>
>>>>> its not returning dentry
>>>>>
>>>>> I again tried after seeing the implementation of vfs_stat function
>>>>>
>>>>> user_path_at(AT_FDCWD, filename, lookup_flags, &path);
>>>>>
>>>>> but this also fails.
>>>>>
>>>>>
>>>>> I am using a proc interface to pass the filename, and copying the
>>>>> filename into a kernel buffer.
>>>>>
>>>>> How can I get a copy of vfs inode for a file name.
>>>>>
>>>>>
>>>>> Need to use vfs_path_lookup for this, present in fs/namei.c file,
>>>> which would give you filled nameidata nd that contais inodes pointer.
>>>>
>>>>> --
>>>>> Regards,
>>>>> Rishi Agrawal
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Kernelnewbies mailing list
>>>>> Kernelnewbies at kernelnewbies.org
>>>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>>>
>>>>>
>>>> - Rohan
>>>>
>>>
>>> vfs_path_lookup needs a dentry/mountpoint for the current path.
>>>
>>> How will I get those.
>>>
>>>
>>> /**
>>>  * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount
>>> pair
>>>  * @dentry:  pointer to dentry of the base directory
>>>  * @mnt: pointer to vfs mount of the base directory
>>>  * @name: pointer to file name
>>>  * @flags: lookup flags
>>>  * @path: pointer to struct path to fill
>>>  */
>>>
>>>
>>> --
>>> Regards,
>>> Rishi Agrawal
>>>
>>> If you dont have vfsmount's ptr, then you can make use of kern_path api
>> with the LOOKUP_FOLLOW as second parameter. This will return the struct
>> path ptr which contains vfsmount and the dentry's ptr. Now the dentry's ptr
>> will contain the inode that you require.
>>
>> - Rohan
>>
>
> Thanks, used that and its working now
>
> --
> Regards,
> Rishi Agrawal
>
> Good to know :)

- Rohan
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